What is the feature numbered 2 in the upper left part of this figure? 
Definitions:
Macrophages
Large white blood cells that are part of the immune system and digest foreign particles and pathogens, playing a role in both innate and adaptive immunity.
Immune System
The body's defense mechanism against foreign pathogens, including microbes, viruses, bacteria, and other invaders.
Behavioral Medicine
An interdisciplinary field combining both medical and psychological knowledge to treat, manage, and prevent health problems through behavioral and lifestyle changes.
Health Psychology
A branch of psychology focused on how biological, psychological, and social factors affect health and illness.
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